package com.test.aqs;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.atomic.AtomicStampedReference;

/**
 * ABA问题的解决
 *
 * AtomicStampedReference
 *
 */
public class ABADemo {
    static AtomicReference<Integer>  atomicReference = new AtomicReference<>(100);
    static AtomicStampedReference<Integer> atomicStampedReference = new AtomicStampedReference<>(100,1);

    public static void main(String[] args) {
        System.out.println("===============以下产生ABA问题===================");
        new Thread(()->{
            atomicReference.compareAndSet(100,101);
            atomicReference.compareAndSet(101,100);
        },"t1").start();

        new Thread(()->{
            //暂停1s，保证t1完成了一次ABA操作
            try {
                TimeUnit.SECONDS.sleep(1);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(atomicReference.compareAndSet(100, 2019) + "\t" + atomicReference.get());

        },"t2").start();

        try {
            TimeUnit.SECONDS.sleep(2);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("===============以下解决ABA问题===================");

        new Thread(()->{
            int stamp = atomicStampedReference.getStamp();
            System.out.println(Thread.currentThread().getName()+"\t 第一次版本号: " + stamp);
            try {
                TimeUnit.SECONDS.sleep(1);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            atomicStampedReference.compareAndSet(100,101,
                    atomicStampedReference.getStamp(),atomicStampedReference.getStamp()+1);
            System.out.println(Thread.currentThread().getName()+"\t 第2次版本号: " + atomicStampedReference.getStamp());
            atomicStampedReference.compareAndSet(101,100,
                    atomicStampedReference.getStamp(),atomicStampedReference.getStamp()+1);
            System.out.println(Thread.currentThread().getName()+"\t 第3次版本号: " + atomicStampedReference.getStamp());

        },"t3").start();

        new Thread(()->{
            int stamp = atomicStampedReference.getStamp();
            System.out.println(Thread.currentThread().getName()+"\t 第一次版本号: " + stamp);
            try {
                TimeUnit.SECONDS.sleep(3);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            boolean b = atomicStampedReference.compareAndSet(100, 2019,
                    stamp, stamp + 1);
            System.out.println(Thread.currentThread().getName()+"\t 修改结果： " + b
                    + ",当前版本号: " + atomicStampedReference.getStamp()
                    + ",当前最新值: " + atomicStampedReference.getReference());


        },"t4").start();
    }
}
